I would definitely get to the rheumatologist. When I went with a headache to the ER they had no idea what to do with me. At that time my blood work was ok. You could go to your primary for blood work ( especially CRP and Sedimentation levels). A couple of weeks later, my blood levels were not good. It took 4 months to diagnose GCA. If anything else changes dramatically, definitely get to the ER. My best to you.

Hi @issyb, Can you get a message to the rheumatologist or primary care physician to advise of your new symptoms quickly? A medical textbook I have advises that prednisone be increased in a person exhibiting symptoms of GCA even before a biopsy of the temporal artery is done. When I was first diagnosed with GCA a doctor told me if I had any pain in my eyes or trouble seeing to immediately go to the emergency room.
My mother-in-law had GCA as well and her symptoms were different from mine, so I never imagined I had GCA. I had short stabbing pains on the right side of my face, from the ear to the nose that came and went, a constant stiff neck, and a tender scalp, for a couple of weeks. Also I had some vision problems in my right eye that came and went a couple of times a few months before I was diagnosed.
If you can't get a hold of your doctors, it's probably best with your symptoms to err on the side of caution and go to the emergency room because the consequences of untreated GCA are stroke or blindness. Good luck!